FR2517248A1 - PROCESS FOR THE MANUFACTURE AND TREATMENT (COOLING) OF A TUBULAR FILM IN EXTRUDED RESIN - Google Patents

Abstract

PROCESS FOR THE MANUFACTURE AND TREATMENT OF A TUBULAR FILM IN WHICH A MOLTEN RESIN IS EXTRUDED BY AN EXTRUSION DIE 1 IN THE FORM OF A TUBE INFLATED BY AN INTERNAL PRESSURE, COOLING AIR BEING SPRAYED AT LEAST AT ONE LOCATION BETWEEN THE EXIT OF EXTRUSION 4 AND THE NEIGHBORING OF A TUBE INFLATION CESSATION POINT, IN THE OPPOSITE DIRECTION IN ORDER TO COOL RESIN TUBE 4, THIS TUBE THEN COLLECTED CONTINUOUSLY. ACCORDING TO THE INVENTION, THE COOLING AIR IS PROJECTED NOT ONLY IN THE DIRECTION OF THE EXTRUSION OF THE RESIN BUT ALSO IN THE OPPOSITE DIRECTION BY MEANS OF AN ANNULAR AIR SPRAY DEVICE 11 HAVING SLOTS 22, 23 IN BOTH WAYS.

Description

The present invention relates to a pro-

  treatment of a tubular film of thermoplastic resin, and it relates more particularly to improvements to a method for cooling a molten resin extruded by an extrusion die. For blown film forming, for high speed forming (high extrusion), to improve productivity and to obtain

  also a high quality film, it was born

  stop cooling the molten resin to a satisfactory

  doing. In the best known process to date for forming a film by blowing,

  a single air projection device of annulai-

  re arranged on an extrusion die to project

  cooling air in the direction of the extru-

  Resin resin, cooling air being blown by means of this annular air projection device on the outer peripheral surface of the molten resin which has been extruded in a tubular form. However, in the forming method of the type described, a stream of hot air, which has been heated to a high temperature by heat exchange with the molten resin at high temperature immediately after the extrusion of the resin by the die, accompanies the

  external peripheral surface in the path of the resi-

  ne for a prolonged period, thus preventing ensuring a satisfactory cooling effect of the tubular resin In addition, if the output flow of the cooling air is increased to enhance the cooling effect, the stability of the forming is considerably g 8 born and therefore a limit has

  naturally imposed on cooling improvements

  ment in the process of the type described.

  We have now proposed a method in the-

  which provision is made for the use of two annular air projection devices to project cooling air in the direction of extrusion of the resin, in two stages in the vertical direction (as described in Japanese patents NO 146764/78 and 14295/82, and another method in which there is provided a vacuum attraction device arranged between the above-mentioned annular air projection devices arranged in two stages, and a current of hot air at high temperature heated by the outer peripheral portion of the tubular resin - is thus separated from the outer peripheral portion of the resin by means of this vacuum attraction device (patent

Japanese NI 29370/79.

  However, in the method described above, the mechanisms are complicated, in particular in the case of a device for attraction by depression it is

  necessary to use a large installation

  The control of the operation is difficult to ensure and stable forming at high speed is not easy to obtain. In addition, apart from the methods described.

  above, we know for example a cooling process

  of a tubular resin by means of water, from the outside or the inside, but, as indicated above, the installation is very complicated and the control

  has proven to be very difficult to ensure.

  The object of the invention is to provide a method of treating a tubular film in which no complicated installation is necessary, the implementation of which is easy to ensure and in which, in addition, the cooling effect is high and allows easily obtain high quality film at

great speed-

  To achieve the above goal, according to the

  vention, cooling air is projected towards a tubular resin extruded by a die, at least from a point -located in the vicinity of this die

  to the vicinity of a point where a dilata ends

  tion or swelling y in the direction of the extrusion of

  the resin and in a direction opposite to this extru-

  to prevent a hot draft

  block the resin in its path, and the cooling air

  is projected from a point near a region of expansion or swelling which is a region

  requiring extreme cooling, in order to cool

thus say the tubular resin.

  Other features and benefits of

  the present invention will emerge from the description

  given below, taken with reference to the drawings an-

xed, on which:

  Fig l is a sectional view showing the agen-

  cementing of a forming apparatus to which a first form of implementation of the tubular film forming method according to the invention is applied; Fig 2 is a larger sectional view

  scale showing an example of construction of the device

  annular air projection used in the appliance

  reil supra; Fig 3 is a sectional view on a larger scale still showing the essential parts of the annular air projection device; Fig 4 is an enlarged sectional view

  scale showing another example of the canceling device

  air projection re used in the forming apparatus

  mage, and Figs 5 to 9 are sectional views showing

  the arrangement of forming devices to which

  plicated the variants of the invention -

  Fig l shows the arrangement of the forming apparatus to which the first mode of application is applied

  implementation of the tubular film treatment process

  area according to the invention In this FIG.

  the melt 3 is continuously extruded through an annular slit

  milk 2 of an extrusion die 1 so as to form

  a resin tube 4 In this resin tube 4 is

  closed compressed air under a certain predetermined pressure by an air passage 5 of the extrusion die. Due to the pressure of this air, the

  resin tube 4 is expanded according to a ratio of

  predetermined alignment, then clamped by cylinders of

  pinch (not shown) which, if represented

  felt would be placed at the top of the drawing, following cooling and solidification of the tube 4

  of resin thus expanded which is then wound in con-

  held at a predetermined speed.

  Among the materials used for resin 3, there will be mentioned conventional thermoplastic resins

  including low density polyethylene, poly-

  crosslinked low density thylene, high polyethylene

  density, polypropylene, polystyrene, copoly-

  mother of ethylene vinyl acetate, poly chloride

vinyl and the like.

  The tube 4 of resin extruded by the die 1

  has roughly the same diameter in its displacement

  ment of die 1 to a point at a predetermined height and is rapidly expanded in a region of expansion or swelling, and a cooling line F appears on the resin immediately

  before a point where the dilation or swelling stops.

  In the remainder of this description, the expression

  "stopping point of expansion or swelling" should be understood as designating a point where the tube 4 of resin reaches a final diameter of a predetermined value after the tube 4 whose diameter increases in the

  dilation or inflation region completes its dilation-

  tion, and the expression "cooling line F" should be understood as designating a limit zone where a rapid change in transparency of the tube 4 is

  visible from the outside, this limit being formed when

  that the resin tube which has been extruded by the die 1 passes from the molten state to the solidified state A central core or core 6 in the form of a column, fixed on the die

  extrusion 1 is provided in the tube 4 This central core

  tral 6 can for example be as described in the

  Japanese Patent No. 46296/80, or the like.

  An annular projection device 11

  air is placed in an intermediate position

  tre the die 1 and the cooling line F so as to surround the tube 4, and the height of the device

11 is adjustable.

  As shown on a larger scale in FIG 2, the annular projection device 11

  air comprises a hollow annular element 13 which pre-

  feels in cross section a roughly

  square, which constitutes the body of the device and delimits

  an annular path or duct 12 for air A pipe 14 for supplying air through which air for cooling the thermoplastic resin is supplied to the annular duct 12 is connected to the hollow annular body 13 The internal peripheral edge 15 of the body 13 includes

  a threaded portion 16 over its entire circumference-

  ce and the middle part of the internal peripheral edge 15 has an air outlet opening 17 having

  a predetermined width in the circumferential direction.

  A fileta-e formed on the peripheral edge

  outer of an upper annular plate 18 is engaged

  ge in engagement with the threaded part 16 located in the

  direction of resin extrusion on the peripheral edge

  internal risk 15, with respect to the opening 17 of the outlet

  air tie, i.e. at the top in con-

  stunning design, while a thread formed on the

  outer peripheral edge of an annular plate

  19 is engaged with the threaded part

  16 located on the opposite side 8 with respect to the direction of extrusion

  resin, so that the air coming out

  through the opening 17 is guided towards the intermediate part

  diary of the hollow annular body 13 An annular plate

  re 20 separator is arranged between the upper plate

  upper 18 and lower plate 19 Perimeter edge

  internal ring of the separating plate 20 protrudes slightly beyond the upper plate 18 and the

  lower plate 19 towards the intermediate part

  dull of the hollow annular element 13, and this edge

  end has a protruding rim 21 which

  pass up and down from a pre-

  determined. The external peripheral edge of the separation plate 20 is located in the middle part of the air outlet opening 17 and the plate 20 is fixed to the body 13 by means of several

  fastening 21 A which are formed at predetermined intervals

  terminated in the circumferential direction on the outer peripheral edge of the plate 20, whereby the air leaving through the opening 17 is separated into two

by the separation plate 20.

  The air passing through a space delimited by the separation plate 20 and the upper plate 18 is projected by an outlet slot 22 directed upwards which constitutes an outlet slot for the cooling air delimited by the internal peripheral edge of the upper plate 18 and flange 21

  projecting and which is directed in the direction of the extru-

  resin, while the air flowing through the space delimited by the separation plate

  20 and the bottom plate 19 is projected by a window

  outlet 23 directed downward which constitutes a cooling air outlet slot directed into

  the opposite direction to that of the resin extrusion.

  In addition, the widths of the outlet slits 22 directed upwards and 23 directed downwards can be varied in a contiranous fashion either by widening them or by narrowing them, by adjusting by screwing the positions of the upper plates and

  lower 18 and 19 on the threaded part 16 respec-

  tively, so that the amounts of air projected from the upward-facing slot 22 and downward-facing slot 23 can be continuously adjusted. Fig 3 shows in more detail a preferred embodiment of the slots 22 and 23 of the annular air projection device ll in the case where it is arranged in a position closer to the lower part of the drawing, it that is to say on the side of the extrusion die 1, that of the swelling region, as is the case in this embodiment.

  Following this example, the report of a lar-

  gor A of the edge 21 projecting in the direction of the extrusion of the resin, and of a width B of the edge 21 projecting

251? 245

  in the direction opposite to the resin extrusion is appropriately changed to a preferred value depending on the resin to be used and

  the forming process (form of swelling) and others.

  An interval M between the upper plate 18 and the separation plate 20 and an interval N between the lower plate 19 and said plate 20 are approximately in the ratio of k LM / N 4 110 Furthermore the angles indicated by X and Z in the drawing are about 750 and an angle such that the angle Y in the drawing is roughly

  450, so that the air flow will cool

  projected by the exit slit 22 directed towards

  the top is tightened to be oriented.

  We will now describe the operation of the

present embodiment.

  The resin tube 4 extruded by the die 1 is cooled by the cooling air projected downwards through the outlet slot 23 directed downwards from the annular air projection device 11, that is to say in the direction opposite to the extrusion of the resin In this case, heated air above

  of the extrusion die 1 is driven from the neighbor

  swims from the outer periphery of the resin tube 4 with the air expelled downwards by the device 11 so as to prevent the heated air from surrounding the periphery of the

  tube 4 and accompany it in its path.

  The resin tube 4 after being extruded by the die 1 has a low melting tension and is effectively cooled by the outlet slit 23 directed downwards, so that the melting tension gradually increases in the direction of extrusion of the resin, so that a stable state thereof can be maintained even in the case of high speed forming.

  The resin tube 4 which has passed the dispo-

  annular jet air projection 11 is again cooled by the cooling air expelled from the upwardly slit 22 and is expanded or inflated in the swelling region, and a cooling line P is formed in a predetermined position

  on this swollen part In this case the cooling air

  dissement is projected against the swollen part which requires extreme cooling from a short distance, and consequently the cooling air

  which is at low temperature and whose speed of flow-

  is not weakened is projected against the swollen region In addition, above the device 11 there do not occur any conditions in which the air which has been heated by the tube 4 below the device 11 follows the outer periphery of the tube 4 Consequently, the tube 4 as a whole is effectively cooled by the air projected by the outlet slit 22 directed

to the top.

  As described above, the tube 4 is effi-

  cacement cooled above and below the device

  ring 11 respectively and the cooling line

  ment F is maintained in a predetermined position

  even during high speed production.

  The position in which the device 11 is placed is adjustable at the intermediate point between the extrusion die 1 and the cooling line F and it can be placed in an appropriate position depending on the type of resin extruded, the conditions

  However, as in the pre-

  feels example, when cooling is assured

  by means of the device 11 having a small diameter

  compared to that of tube 4 after completion

  ment of its expansion, if the position of the

  device 11 is too close to die 1, the re-

  cooling by means of slot 23 is not

  dyed satisfactorily; on the contrary if the posi-

  tion of the device 11 is too close to the cooling line F, there is then a possibility that the device 11 comes into contact with the tube 4> thus risking impairing stability Consequently the normal position of the device 11 is preferably

  set in the range of 1, H -19 H, or H is a high

  tor of the extrusion die with respect to the cooling line F.

  To adjust the amounts of cooling air

  projection projected by the device 11 in the direction of the resin extrusion and in the opposite direction, the upper plate 18 and the lower plate 19 must be turned relative to the hollow body 13

  of the device, respectively, so that the lar-

  geurs of the slit 22 directed upwards and of the slit 23 directed downwards can be adjusted respectively. In the present example with the arrangement described above, the resin can be cooled by

  very efficiently and there is no shortage of

  sance of cooling and unevenness in the cooling conditions even during high speed forming, and irregular inflation (i.e. the diameter of the resin tube is

  irregularly increased or decreased) and a shift

  zigzag cement are prevented from occurring, and the advantage is obtained of being able to manufacture a film devoid of irregularities in thickness and width,

  wrinkles and the like, stably with a pro-

he

high ductivity.

  In addition, the resin tube 4 can be re-

  cooled satisfactorily even during forming at

  high speed, so that the cooling line

  ment F can be kept in a predetermined position Consequently there is no possibility of

  blocking by clamping cylinders.

  It is common practice for the resin

  fondue 3 used in this method of implementation

  vre or a thermoplastic resin It is possible to obtain satisfactory cooling of a low density polyethylene having a low melting voltage, of polypropylene etc., the forming of which at high speed

  and in great thickness is difficult, and polyethylene

  ne high density and the like, in which the height of the cooling line P must be increased so that the high speed forming of the above resins can be carried out stably with a

high productivity.

  In addition, the quantities of cooling air

  projected in the direction of resin extrusion and in the opposite direction, and the air projection angles can be easily adjusted, independently of each other and continuously by adjusting the positions by screwing on the threaded part 16 of the upper 18 and lower 19 plates Consequently

  the cooling conditions can be easily obtained

  optimally depending on the type of resin,

training conditions and others.

  A description will be given below.

  cut out of the present mode of implementation of the invention

  tion with reference to comparative examples.

Examples 1 to 5

  High density polyethylene was extruded (density 0.955 g / cm 3, melt index 0.05 g / 10 min)

  by means of a die 1 comprising a canceling slot

  re 2 having a diameter of 80 mm in an extruder having a bore diameter of 55 mm, and a blown inflated film was formed having a flat width of 550 mm and a thickness of 25 µm In this

  example, we used a central core 6 having a diameter

  95 mm meter and a length of 500 mm.

Forming temperature 20,000 C.

  -roceda cooling: an annular air projection device ll (having an internal diameter of 130 mm) whose air outlet slots 22 and 23 (width A 20 mm, width B 10 mm) are arranged at the same time in the direction of the resin extrusion and in the opposite direction was placed at a point spaced 50 mm from the extrusion die 1 in the first example, at a point spaced 100 mm from the extrusion die 1 in the second example and at a point 200 mm apart from the extrusion die 1 in the third example, between die 1 and the line of

  cooling P of the inflated part, the return air

  was projected both in the direction of

  the extrusion of the resin and in the opposite direction.

  Resin extrudable products that can be formed stably are studied and the results

are given in Table 1.

  Comparative Example 1 The extruded resin products were studied

  can be formed stably in the same con-

  as in examples 1 to 3, except that an annular air projection device is provided on the extrusion die to project air

  only in the direction of the resin extrusion.

  The results are given in Table 1.

Table 1

Report of the quan-

air quantities

thrown by the dis-

  annular positive in the direction of extrusion and

in the opposite direction

sé (meaning of the ex-

trusion: op sense

  example) Example Example i 2 3: 1 4: 1 3: 1

Example

comparative

Distance from the

  positive canceled 50 100 200 O re of the die (mm) Distance of the

cooling line

dissement of the -

die (mm) 400

Extru- products

dice can be formed of

stably

  (kg / hb) l Exemole 4 to 6 With the exception that the flow rate of extruded resin was adjusted to 40 kg / h and that the flat width of the film formed was 400 mm, the forming was

  made using the same resin and the same extru-

  deuse at the same forming temperature as in examples 1 to 3 In this case, the forming stability for the different thicknesses was studied, while the height of the annular air projection device ll is modified and the results are given in the

table 2.

  Comparative Example 2 The forming stability was studied in the same way as in Examples 4 to 6 under the same conditions as in these However the device

  classic ring of air projection (having a diame-

  internal 130 mm) was provided on the die so as to project air only in the direction of the resin extrusion The results are given in

table 2.

  Table 2 Example Example Example Example 4 5 6 comparative

Report of the quan-

air quantities

  thrown by the annular positive 4: 1 3: 1 2: 1 up and down (up: down) Table (continued) Example Example

4 5

Example

*Example

  comparative Distance from the annular ring device 50 100 200 O

of the chain

re extru-

  sion (mm) Distance from die cooling line (mm) Forming stability

for pelli-

thick cules

different sisters

annuities (p?) Good

Unstable

Not for-

mable

Not for-

mable Good Good Good

unstable

Good Good Good Good

Unstable

Not for-

mable

Not for-

mable

Not for-

mable

  It appears from the comparative examples below

  above that the present embodiment allows excellent cooling, stable extrusion at high speed and high extrusion rate, and also also produces a film having a

significant thickness.

  In the implementation of the invention, the

2,51248

  fixing positions of the two upper and lower plates 18, 19 of the annular device II on the hollow annular body 13 through the threaded part 16

  have been made variable However this partial form

  can be replaced by another in which either one of the fixing positions is adjustable or the two fixing positions are adjustable as

  shown in Fig 4 In this case, if adjustment screws

  ge 24 are mounted at predetermined intervals in the circumferential direction on the partition plate 20

  so that the front ends of the retaining screws

  24 are not movable in rotation and axially, and that the adjustment screws are screwed onto the upper plate 18, the rotation of these adjustment screws 24 then makes it possible to simultaneously adjust the two outlet slots 22 directed upwards and 23 directed to the

  low, so that the air quantities projected.

  in the direction of the resin extrusion and in the direction

  opposite and the projection angles are simultaneous

specifically settled.

  The projected cooling air flows

  tee in the direction of resin extrusion and in the opposite direction are not necessarily adjusted by means of the adjustment of the widths of the slots 22 directed upwards and 23 directed downwardsbut can be adjusted

by a mechanism.

  In addition, the slots 22 and 23 are not necessarily made on a single hollow body 13; this means that slot 22 and slot 23 are not

  not necessarily provided on the main body of a device

  air spraying device simultaneously, but this particular form can be replaced by an arrangement in which one of two different bodies of annular air spraying devices arranged contiguous or adjacent is provided with the slot 22 directed towards the

  high, while the other is provided with the slot 23 diri-

down-for example.

  In addition, the central core 6 has been provided in the tube 4 as described above, but this core 6 is not necessarily provided. However, the fact of providing the central core 6 may offer the advantage that

  the forming stability is reinforced even in the pro-

  yielded from tubular film processing of film-

  the very thin at high speed and a film of a

significant thickness.

  The description of

  modes of implementation other than the first described above 'The same references as those used in the first embodiment are used in the other Figs to designate the analogous parts or

  identical, so the detailed description will

simplified or omitted.

  FIG. 5 shows the second embodiment of the invention in which the tube 4 made of resin extruded by the die 1 completes its expansion to a predetermined height and, in the vicinity of this inflation stop point there is provided a annular air projection assembly 31 having a diameter greater than the diameter of the tube 4 after its inflation, that is to say having a sufficiently large diameter and allowing the tube 4 not to come into contact with the device

  annular 31 so that it can be moved vertically 8

  by a vertical drive device not shown In this example, the swelling stop point appears

in a slightly more position

  closer to the direction of the extrusion than to the cooling line

  dissement F In other words, the line F appears

  immediately before the inflation stop point.

  The annular air projection assembly 31

  com Drênd a part 32 arranged downwards and a part

  tie 33 arranged upwards, these parts 32 and 33 being arranged contiguous to each other A slot 34 directed downwards, of part 32 is oriented in the opposite direction to the extrusion of the resins According to the position in which the annular air projection device 31 is arranged and the shape of an inflated part of the tube 4, the slit 34 directed downwards may preferably be inclined between 100 and 70 D and more preferably between 100 and 450 when, normally, the direction opposite to the resin extrusion is set to 0 and an inward direction along the radius

  of tube 4 is set to 90 (see angle OL in Fig 5).

  The cooling air is projected at a neighboring angle within the range of angles described above,

  so that the cooling air flows from the

  positive 31, along the outer peripheral edge of the tube

  4 arranged on the side of the die 1.

  Because the surface of the resin tube 4

  against which the cooling air is directly blown

  slowing projected by the slit-34 directed downwards, is solidified to a certain extent, even if the amount of projected cooling air is increased to a considerable extent, no irregular inflation or zig-zag movement is caused on the resin tube 4, and the forming stability is not

  hampered However, when there is a possibility

  lity to interfere with forming stability, the inclination of the slit 34 directed downwards must be reduced

of an appropriate value.

  The current of hot air which tends to rise, being accompanied by the tube 4 in resin according to the

  outer periphery of tube 4 in the direction of extrusion

  resin, is removed from the first part

  external device of tube 4 by cooling air

  blown against the tube 4 through the slot 34 directed downwards.

  In addition, the annular portion 33 of projection

  tion of air arranged upwards, contiguous to the part 32 directed downwards, as shown in the drawing, has a slot 35 directed upwards to project the cooling air in the direction of the extrusion of the resin, and the cooling air projected by this

  slot 35 improves the stability of the tube 4 in its

  seems. The mode of implementation described above

  of the above arrangement may offer the following advantages:

touts.

  The arrangement is such that the cooling air

  sement is projected in part 32 arranged towards the

  down in a direction opposite to the extrusion of the resi-

  ne, so that the current of hot air generated by the heat exchange with the tube 4 of resin under high temperature immediately after being extruded

  of the die 1 does not accompany this tube, it remains

  both constantly exposed to cooling air under

  low temperature, so that the cooling effect

  ment can be reinforced, thus making it possible to form a high-quality film at high speed. Furthermore, the cooling air is blown against the inflation region requiring extreme cooling, over a very short distance, so that the aforementioned inflation region. can be effectively cooled

  by the cooling air which has not lost its life

flow size.

  Because the surface of the resin tube 4 which is located at the emolacenent o is

  the annular part 32 directed downwards is solidified

  Fans to some extent, even if the amount of air

  proposed rzfroiaissement by part 32 is in Dnen-

  The forming stability of tube 4 is not easy.

  obstructed, so that the amount of cooling air

  can be increased, thus also allowing

  to enhance the cooling effect.

  Even if the position in which the annular device 31 is located is changed in the vertical direction to a significant extent, the forming stability is not impaired and in particular when the

  device 31 is arranged above the termination point

  inflation, forming stability is improved

  to a great extent and thereby the cooling effect

smoothing is not diminished.

  In addition, it is sufficient that a single annular device is provided in the vicinity of the point of cessation of inflation to be able to use a very simplified installation, thereby making it easier to order.

  of operation and handling.

  Since the air is projected through the slit directed upwards in the direction of passage of the resin, the tube 4 is placed in a tubular laminar flow of cooling air similar to its path, so that the stability of the device 31 in the direction of extrusion is improved, which results in improved stability of the tube 4 as a whole. Furthermore, the cooling after inflation is carried out satisfactorily,

  the important advantage is obtained of preventing

  has a blockage of the film in thickness.

  A detailed description will be given below.

  lée of this mode of implementation with reference to

  examples and comparative examples given below.

Example 7

  Low-density polyethylene was extruded continuously through an annular slot 2 having a lip gap of 2 mm and a diameter of 200 mm in a screw extruder having a bore diameter of 50 mm and a ratio L / D = 28 density (density 0.92 g / cm 3, melt index 2.4 g / 10 min) to form a blown film having a flat width

  of 470 mm and a thickness of 30 µm.

Forming temperature 17000.

  Cooling method: the annular assembly 31 comprising the annular part 32 arranged downwards (having a diameter of 390 mm) and the annular part 33 arranged upwards (having a diameter of 390 mm) was disposed at a height of 550 mm by

  compared to extrusion die 1, the cooling air

  -dissement was projected by said assembly 31 following

  : an angle of 200 relative to the direction of the extrusion

  sion of the resin inwards along the radius of the tube 4 in resin and, moreover, at an angle of 450 relative to the direction of extrusion of the resin

  inwards along the radius of the tube 4.

  The results of the property assessment

  are given in table 3.

  Comparative example 3 Using the same resin, the same extrusion die 1 and the same screw extruder as in

  example 7 above we sprayed the cooling air

  ment by the annular device provided on the upper surface of the extrusion die 1 and comprising a cooling air outlet orifice having a diameter of 300 mm at an angle of 45 relative to

  to the direction of resin extrusion inwardly

  laughing along the radius of the resin tube The results are given in table 3. Comparative example 4

  A first annular projection device

  tion of air with a bore diameter of 300 mm is

  provided on the upper surface of the extrusion die

  sion and a second annular air projection device having a bore diameter of 390 mm is provided at a height of 550 mm from the extrusion die Air

  has been projected by these two devices.

  tifs at an angle of 450 relative to the direction of the resin extrusion inwards along the radius of the resin tube The other conditions were similar to those of Comparative Example 3

  results are given in table 3.

Table 3

  Example Example Example 7 comparative comparison Exit of 3 4 formable extrusion (kg / h)> 60 35 60 Stability of forming Transparency of the film formed

Possibility of com-

function order-

  It appears from the examples described above that the present embodiment in which a cooling phase is simply used has an effect equal to cooling in two phases with regard to the forming and stability properties.

  and transparency, and is further superior to the re-

  two-phase cooling as regards the pos-

  high speed control and forming capability

  In addition, provision may be made between the

  annular positive 31 and the extrusion die 1 an annular air projection assembly directed downwards adapted to blow the cooling air in a direction opposite to the extrusion of the resin Have it provided with annular projection assemblies of air that can project cooling air in the opposite direction to the resin extrusion, in two phases, allows more efficient cooling to be effectively carried out with regard to the

resin tube shape 4.

  Fig 6 shows the third embodiment

  sation of the invention in which a device canceled

  the air spraying area 41 is disposed at a predetermined height above the extrusion die 1, the cooling air being projected by a slot

  42 of this device 41 in the direction of the extru-

  resin, so that a first draft of air

  is blown against the resin tube 4.

  In addition, the fact that the annular device

  air 31 shown in the second embodiment-

  above is placed in the vicinity of the termination point

  tube 4 swelling, the cooling air

  thrown through the slot 34 directed downwards and through the window

  te 35 directed upwards constitutes a second current

cooling air.

  The cooling air projected by the slot 42 in the direction of the extrusion, and the cooling air projected by the slot 34 directed downwards in the opposite direction meet at a point located between the upper surface of the die. i and the inflation stop point, and flow by being pushed outward in the radial direction relative to the tube 4, so that the current of hot air

  generated by heat exchange between the cooling air

  the resin tube is driven out of the periphery

outer of tube 4.

  This mode of implementation ensures the advantages

  following stages The cooling air projected by the device 41 is blown against the tube 4 heated to a high temperature which has been extruded from the die 1, and this air is in heat exchange relationship with the

  tube and is heated to a high temperature.

  This stream of hot air thus heated to a high temperature meets the cold air projected downwards

  the device 31 and is driven from the outer periphery

  from tube 4, so that the current of hot air does not accompany the path of tube 4 Consequently

  this tube is constantly exposed to the cooling air

  at low temperatures so that the cooling effect

chilling is important.

  In addition, the current of hot air can be 9

  hunted without the need for a vacuum mechanism

  ration of the hot air flow between the annular devices 31 and 41 arranged in two stages, so

  that this mode of implementation does not require an in-

  tallation of large dimensions, thus facilitating the

process control.

  The surface of the resin tube 4 is solidified

  relied to some extent on the point where the device 31 is arranged, so that the forming stability of the resin tube is not impaired even if the cooling air outlet flow rate of the device 31 is increased, so that the air outlet flow of

  cooling can be increased, thus also allowing

  Also improve cooling As a result we can form a high quality film

high speed.

  This mode of implementation is

  tagous in that the cooling air is blown against the swelling region which is that required

  both extreme cooling by the two available

  annular sitives 31 and 41 over a very short distance "Fig 7 shows the fourth mode of placing

  implementation of the invention in which a device is provided

  annular positive 51 of air projection in the vicinity of the upper surface of the die 1 The outlet slot of this device 51 has a double configuration, inclined from the extrusion of the resin towards the outside and radially with respect to the tube 4 , and

  the cooling air projected by the slot 52

  creates a first stream of cooling air

blown against the tube 4.

  An annular air device 31 is arranged in the vicinity> of the point of cessation of inflation of the tube 4 in the same way as in the third embodiment.

  in use, and this device 31 blows a second

  rant of cooling air against tube 4.

  The fourth mode of implementation comprises

  as the arrangement described above presents advantages

  ges similar to those of the third embodiment plus the following additional advantages Because the air projection slot 52 of the annular device 51 disposed in the vicinity of the upper surface of the die has a double configuration and is inclined

  in the direction of extrusion of the resin outwards

  laughing and radially with respect to the tube 4, even if a resin such as a low polyethylene

  density, high density polyethylene and poly-

  propylene, the device 51 has the effect of drawing the

  tube 4 made of resin extruded by die 1 outwards

  laughing and radially by a venturi effect, and fixes this tube so that the formation stability is

even easier.

  A description will be given below

  detailed description of this mode of implementation with reference to

  Refer to the following examples and comparative examples.

2517-248

  Example 8 A copolymer treated at low pressure with ethylene 4 methylpentene 1 (density 0.923 g / c Im 3, melt index 2, 4 g / 10 min) is continuously extruded using an annular die 2 having an interval between lips of 2 mm and a diameter of 125 mm, in a screw extruder having a bore with a diameter of mm and a ratio L, / D = 28 to form an inflated film having a flat width of 30 mm and a

thickness of 30 µm.

  Forming temperature 17,000 C. Cooling process: the annular device 51 for air projection with double slots

  (diameter 150 mm) was placed in the vicinity of the

  upper face of the extrusion die 1 exterior-

  ment to the air projection slots 52, the exterior slot

  superior projected a stream of cooling air inclined at an angle of 20 outward from

  to the radial direction of the resin tube and to the direction

  tion of the extrusion, and the internal crack projected

  cooling air vertically in the direction

  tion of the extrusion, thus constituting a first

  cooling air supply rant The annular device 31 was furthermore arranged at a point 500 mm above the extrusion die 1, and the cooling air was projected by this device 31 in the direction of extrusion and in the direction

  opposite, thus ensuring the blowing of a second

rant of cooling air.

  The results of the property assessment

  sound forming; given in table 4.

  Comparative example 5 The forming was carried out in the same way as in the aforementioned example 8 except that instead of blowing with a stream of cooling air using the annular air projection device 31, a device air projection ring is

  say Dose in the vicinity of the stop point of inflation

  to spray cooling air only-

  ment in the direction of extrusion, and a second stream of cooling air is projected by this device the results are given in table 4. Comparative example 6 The forming was carried out in the same way as in Example 8 aforementioned except that a first annular air blowing device (diameter

  300 mm) was placed in the vicinity of the upper surface

  of the extrusion die, a second annular air blowing device being placed at a point 500 mm above the extrusion die, cooling air was projected from these first and second devices into a direction inclined inwards relative to the radial direction of the tube and to the direction of the resin extrusion,

  thus ensuring the blowing of a first and a

  cond cooling air currents The results

are given in table 4.

Table 4

example

Example

comparative

*Example

  comparative Forming stability O Extruded outlet 5 formable (Kg / h) 5,403 _

Cooling effect

  ment f. Clarity:, lx 9 9 8 Brillantd: 2 x 102 106 100 Tear resistance 98/248 99/219 112/212 MD / TD Kg / cm 3 x? I 3 x _ _ _ _ Ao Impact resistance 2490 2630 2680 m (Kg cm / cm) 4 xo A Puncture resistance 15000 13800 13800 o tion (Kg cm / cm) 5 xmii Ar, - $ S ocie ty For lx: Clarity according to norm ASTM: D 1003 (seseg M aterials 2 x: Brilliant according to ASTM D 523

  3 x: Tear resistance according to Japanese standard

  naise JIS Z 1702 (Japanese Industrial Standard) 4 x: Impact resistance A film was fixed on

  an annular support and was perforated in use

  a pendulum with a 25.4 mm shock head,

  and the value of the energy required for the perfo-

  ration was measured (proceeded from the shock on film-

  le) The test apparatus used was an apparatus

  impact test eye manufactured by the firm Japo-

born TOYO SEIKI SEISAKUSHO.

  5 x: Puncture resistance according to standard

Japanese JIS P 8134.

  It appears from the above examples and from the comparative example that according to the present mode of implementation of the invention the cooling effect

  obtained is high, the forming of a high extru-

  This can be done in a stable manner and moreover, no precise alignment is necessary because of the height of the location of the annular air blowing device 31 which is not precisely imposed,

  thus facilitating the operation.

  Fig 8 shows the fifth setting mode.

  work of the invention in which the central core 6 -

  and the annular air projection device ll are provided in the same way as in the first embodiment, but which differs from this in that an annular air projection device 61

  is arranged in the vicinity of the inflating stop point

  ment, and the cooling air is projected by an outlet slot b 2 of the device 61 in the direction opposite to the extrusion of the resin, thus ensuring the blowing of a second stream of cooling air

against tube 4.

  According to this fifth embodiment, even if the change in diameter in the swollen part

  of tube 4 is fast, the inflated part can be cooled

  die satisfactorily, that is to say that the tube 4 can be effectively cooled independently of its shape since the cooling air is projected against the inflated part both through the slot 62 and

  through the slot 22 directed upwards respectively.

  Fig 9 shows the sixth embodiment of the invention in which the same arrangement is used as in the fifth example, except that instead of the annular device ll the device 31 is used. This sixth mode of implementation with the arrangement described above has advantages

  similar to those of the fifth embodiment.

  In addition, in the fifth and sixth embodiments, the annular device 61 comprising the outlet slot 62 directed downwards can be

  replaced by device 11 or device 31 pre-

  cited can project the cooling air both upwards and downwards In this case, the tube 4 after its inflation is arranged in a tubular laminar flow of projected cooling air

  by device 11 or device 31 in the direction

  extrusion of the resin, so that the stabili-

  the forming unit is further improved, so that the tube 4 after inflation can be effectively cooled,

  thus eliminating the possibility of a block

  cage in the case of a film of significant thickness.

  It has been described in the foregoing the case in which the method of treating tubular film according to the invention is applied to forming upwards, but the method can also be applied

  when forming downwards or laterally The pro-

  yielded is not necessarily applied to forming a film in a single layer but can also be

  applied to forming a multi-layer film.

  In addition, the annular devices 11 or 31 include means for adjusting in the vertical direction.

  but these means are not necessarily provided Ce-

  while providing vertical adjustment allows

  easily adjust the position of the devices

  parts 11 and 31 and in addition the position of these arrangements

  tifs in the vicinity of the upper surface of the extrusion die at the beginning of the operation and then can be gradually raised according to the rise of the inflated part of the tube 4 to finally reach

  a predetermined position, thus allowing a function

  regular training from start to forming

stable.

  As described above, the invention provides a method of processing tuoular film requiring no complicated installation, the operation of which is easy, the cooling effect

  l high and allowing easy training at high vi-

  weaves a high quality film.

Claims (14)

f CLAIMS   1 A method of manufacturing and processing a tubular film, in which a molten resin is extruded by an extrusion die (1) under a tubular form, inflated by internal pressure and continuously collected, characterized in that the cooling air   is projected both in the direction of the former   trusion of the resin and in the direction opposite to this extrusion, at least in a position located between a point close to the extrusion die (1) and a point of cessation of inflation of the film in order to cool thus the tubular film.   2 The method of claim 1, wherein the projection of the cooling air is provided by an annular air projection device (11, 31) in which are provided slots (22, 23,, 34) for projecting air so as to direct air both in the direction of resin extrusion and in the opposite direction.   3 Method according to claim 2, character-   risé in that the air outlet flow from at least one of said air projection slots (22, 23, 35, 34)   directed in the direction of the extrusion and in the direction   opposite is continuously adjustable.   4 Method according to claim 1, character-   risé in that the cooling air is projected in the vicinity of said point of cessation of swelling of the tube.   Method according to claim 1, characterized in that the projection of the cooling air is carried out at a point situated between the vicinity of the   extrusion die (1) to a cooling line   ment (P) located immediately before the point o stops swelling of the tube.   6 Method according to claim 5, character-   risé in that the cooling air is projected in a range of 0.1 H 0.9 H o H is the distance from the extrusion die (1) to the cooling line- ment (F).   7 A method of manufacturing and treating a tubular film in which a molten resin is extruded by an extrusion die in a tubular form, swollen by internal pressure and then collected continuously, a process characterized in that air cooling system is projected at a point located in the vicinity of said extrusion die (1), in the direction of extrusion to thereby ensure a first   cooling of the tubular resin, the return air   being cooled projected at a predetermined point relative to the point of projection of the first stream of cooling air in the vicinity of a point of cessation of swelling of the film, both in   the direction of the resin extrusion and in the di-   opposite rection to ensure a second current   resin tube cooling air   8 Method according to claim 7, character-   rised in that said second cooling is carried out using an annular air projection device (11, 31) in which slots (22, 23, 35, 34) are oriented both in the direction of the extrusion of   the resin and in the opposite direction.   9 Method according to claim 8, character-   risé in that the air output rate of at least one of said slots (22, 23, 35, 34) of air projection of the annular device (11, 31) directed in the direction of extrusion and in the opposite direction is adjustable continuously.   process according to claim 7, charac-   terized in that said second cooling is effected   killed at a point near the cessation point swelling of the resin tube.   11 The method of claim 10, charac-   terized in that said first cooling is ef-   made using an annular device (51) having two air projection slots (52) oriented in the   direction of resin extrusion.   12 Method of manufacturing and processing a tubular film in which a molten resin is extruded by an extrusion die (1) in a form   tubular and inflated by internal pressure and re-   then collected continuously, characterized in that the cooling air is projected at a predetermined point between the vicinity of the extrusion die (1) and a swelling region of the resin tube (41 both in   the direction of the extrusion and in the opposite direction   sée in order to ensure a first cooling of the resin tube, cooling air being projected in a position located in the vicinity of a point of   ceasing of swelling of the resin tube (4), in the di-   rection opposite to the extrusion of the resin to ensure   rer a second cooling effect of the resin tube.   13 The method of claim 12, charac-   terized in that said first cooling effect   is insured using an annular pro-   air junction (11, 31) comprising projection slots   tion of air (22, 23, 35, 34) which are directed both in the direction of the resin extrusion and in the opposite direction.   14 The method of claim 13, charac-   terized in that the air outlet flow rate of at least one of said air projection slots of the annular device (11, 31) directed in the direction of extrusion of the resin and in the opposite direction is adjustable continuously.   15 The method of claim 12, characterized in that the second cooling effect is carried out at a point located in the vicinity of said point   stop swelling of the resin tube.   16 The method of claim 15, charac-   terized in that to ensure the second cooling effect   cooling air is also projected   tee in the direction of the resin extrusion.